Device for detecting synchronism



1 May 12, 1925 C. F. JENKINS DEVICE FOR DETECTING SYNCHRONISM Filed Feb. 19, 1923 Patented May 12, 1925.

I '1",537,oss PATENT OFFICE.

CHARLES FRANCIS ENKINS, OF WASHINGTON, DISTRICT OF COLUMBIA, ASSIGNOR T0 JENKINS LABORATORIES, OF WASHINGTON, DISTRICT OF COLUMBIA, A CORPORA- DEVICE FOR DETECTING SYNCHRONISM.

Application fled l'ebruary 19, i923. Serial No. 619,995.

To all w/wm it may concern:

Be it known that I, CHARLES Franc s JENKINS, citizen of the United Statesg'residing at Washington, District of Columbia, have invented certain new and useful Improvements in a Device for Detecting Synchronism, of which the following is a specif fication. This invention relates to apparatus used in the broadcasting of radio pictures, and

' has for its principal object to provide means for determining whether the rotation of the prismatic rings at the sending station are station,

in' synchronism with the rotation of the prismatic rings at the receiving station,- means hereinafter disclosed, and particular- 1y-pointed out in theclaims.

In the accompanying drawin s lji'g. L is the sending station, and Fig. 2 the receiving station. Like symbols refer to like parts in both figures,'in which A is a pair of mains from any source of electric power, B a motor for producing thenecessary rotation at each C a make-and-break device mounted on the motor shaft, and D a rheostat for regulating the speed of the motor. E is a coil F, the contact G, and, the battery H. J is-a contact initially employed to maintain the motor at a constant speed (disclosed in application Serial 607,614).

L is an induction coil, the primary of which is in the circuit L, K (battery), J and E; while the secondary is in the antenna-ground circuit (N, P, Fig. '1).

In Fig. 2 the antenna-ground circuit is closed through the primary of induction coil L, the secondary of which is in circuit with the actuating coil of the relay R. Thesec- D to a speed which is known to be somewhatless than the natural period of the tuning fork E. The rotation of the armature, and consequently the rotation of the doublebreak contact C mounted on the end of the armature shaft, is not effected by the fork when the latter is not in vibration. When, however, the tuning fork isput into vibration, opening and. closing the contact J, a

the

circuit of this relay includes the second circuit for the armature current is provided whenever the, contacts at C, and the contact at J occur simultaneously. This short circuits the resistance 1), and the motor immediately increases .in' speed until the make-and-br'eak at the two points, "C and J,

occur at slightly different times, which, as.

explained above, leaves the circuit open and produces no effect on the motor. This is explained in the application above referred to (607,614) ,andhas no interest here, except as it explains that the vibration of the fork determines with a very sharp degree of accuracy the rotation of the motor.

livery contact breakat J through the battery K, and the primary of the transformer L, sends out a sha impulse from the antenna N, and these picked up by the antenna at the receiving station, creates a corresponding momentary. current through the secondary circuit of the inductioncoil L, in which circuit the coil of the relay R is included. This then actuates the relay, which in turn opens and closes the contact at U, causing the lamp to flash witheach break of the contact J at the sending sta- 'tion.

Asthe lamp'S at the receiving station is located in such a manner that it intermittently-illuminates the I-shaped contact member C, it is obvious that if the illumination occurs with each revolution, or half revolution, of the I-shaped piece, the same will appear to stand still no matter how rapidly it may be rotating.

As the impulses which light the lamp S at the receiving station are sent out by the vibrations of the tuning fork E at the broadcasting station, it is obvious that when the I-shaped piece appears to stand still'it means that the two forks, i. e., the fork at the sending, and the fork at the receiving stations, are in exact synchronism, because the fork at the receiving stat-ion is controlling its motor in the same way that the fork at the sending station is controlling its motor.

If, however, the I-shaped piece appears to rotate slowly to the right or to the left, it indicates that the tuning fork of the receiving station is vibrating slightly too fast or too slow, and, therefore, should be ad justed to "bring its period into exact synchronism with the period of the fork at the sending at on, This can be done by any of the usual methods, as, for example, the movement of the weights ac and y.

It is quite obvious that greater sensitivity and greater power might be obtained in the various circuits in the usual manner, for example, by employing suitable additional coils, condensers, amplifying tubes, etc., Without departing from the invention disclosed herein, and that other uses may be found therefore; nor is the particular hookup disclosed necessarily the best.

What I claim, is

1. The combination of a motor, means for transmitting to a distance signals having a definite relation to the revolutions of said motor, a distant second motor, a visible marker on the rotor of said second motor, a lamp for illuminating said marker, and means for lighting said lamp in synchronism with the incoming signals.

2. The combination of a vibrating fork, means for transmitting to a distance a signal for each vibration of said fork, a distant second vibrating fork, controlling the movement of a visible marker, a lamp for'illuminating said marker, and means for lighting said lamp in synchronism with .the lncoming signals.

3. The combination of a vibrating fork kept 'in vibration by electrical make-andbreak contacts, means for transmitting to a distance a signal for each contact, a distant second vibrating fork, an intermittently lighted lamp at the location of the second fork, said lamp being lighted at each contact of the first mentioned fork.

In testimony whereof I have afl lxed my signature.

CHARLES FRANCIS JENKINS. 

